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Camera quality is a competitive area for the current crop of smartphones. With each new device, the gap between phones that happen to have cameras, and actual point-and-shoot cameras, shrinks.

To accurately see how good the iPhone 4's 5-megapixel new camera really performs, we put it through the same battery of tests we use for point-and-shoot digital cameras, and rated it against other cutting-edge smartphones, including the new Droid X.

The iPhone's camera stats

The iPhone camera is 5-megapixels, but as Steve Jobs pointed out in his WWDC keynote, megapixel count alone doesn’t equal good images. Two of the smartphones we tested against the iPhone had higher megapixel counts, but they still scored lower on image quality tests.

The reason for the discrepancy? The iPhone packs its 5 million pixels onto a 1/3.2-inch backside-illuminated CMOS sensor. Sensors with backside illumination technology move the wiring from the front side of the sensor to the back, so that it’s behind the light sensors. This allows more light to reach the sensors without being diffused by the circuitry, which means the camera can capture better low-light images.

Another factor contributing to the camera’s good low-light performance is the size of its pixels. Bigger pixels capture more light, which makes for better images. Apple retained the same pixel size that it had on previous iPhones instead of shrinking them down to fit more megapixels into a smaller area, which is something many cameras do to inflate their megapixel count.

As on many smartphones (including previous iPhones), the iPhone 4’s 3.85mm camera lens has a fixed aperture of f/2.8, and automatically adjusts the shutter speed and ISO to get the best exposure. In our tests, we managed to make the ISO go as low as 80, and as high as 1000. The longest exposure time was 1/15 of a second, and the shortest was 1/10000 of a second.

The iPhone 4 is still very light on camera controls, especially compared to a smartphone like the EVO 4G which allows you to manually adjust settings such as white balance, ISO, and exposure compensation.

What the iPhone 4 has is the same tap-to-focus feature that debuted on the 3GS—tap anywhere on the screen and the camera will focus on that point and adjust the exposure for that spot. There’s a 5x digital zoom slider, which essentially crops your image in-camera. There is a new LED flash which can be set to Auto, Off, or On. You can toggle between the main camera and the new .3-megapixel front-facing camera. Tap-to-focus works on the front camera, but digital zoom does not.

If you switch over to Video mode, you’ll be able to use the same controls. While a video is recording, you can turn the light on and off, and tap the screen to change your focus from one subject to another. Double tapping on the screen zooms in so that your video fills the entire screen, though it is still recording at the same 1280 by 720 size. The iPhone records 720p HD video at 30 frames per second (fps) and the front facing camera records 360p video. You cannot toggle between the two cameras while it is recording.

About the lab tests

We compared the iPhone 4’s camera with an iPhone 3GS, three other smartphone cameras, and two pocket point-and-shoot cameras. For the video portion of the test, we threw in a Flip Video M2120 for good measure. The other smartphones we tested were the EVO 4G, the Droid X, and the Samsung Galaxy. The point-and-shoot cameras tested were the Sony DSC-WX1 and Samsung HZ35W.

For the still image tests, our lab took the same four photos with each camera. Without knowing which camera each photo was from, a panel of judges rated the images for exposure quality, color quality, sharpness, and distortion amount. The ratings were compiled and averaged for each category, and then used to calculate a final image quality score.

For the video tests, the lab recorded two clips with each device—one in low-light and one in regular light. Our panel then rated each clip’s video and audio quality.

Image quality rankings

Click to see a larger image comparing a sample photograph from each camera.Unsurprisingly, the two point-and-shoot cameras came in first in our image quality tests. The next best camera, and the highest scoring of all the smartphone cameras that we tested, was none other than the iPhone 4. Next in the rankings was the Droid X, followed by the EVO 4G, the Samsung Galaxy, and way at the bottom, the iPhone 3GS.

The iPhone 4 had, by a healthy margin, the best exposure and color scores of the entire bunch, beating out even the point-and-shoot cameras. It did run into trouble in the sharpness and distortion categories, performing much lower than the pocket cameras and similarly to the Droid.

These scores show that megapixel count isn’t the most imporant factor when it comes to quality, as camera manufactures sometimes claim it is. The Droid X and EVO 4G both have 8-megapixel cameras, and the Samsung Galaxy has a 5-megapixel camera. As for the point-and-shoot competition, the Samsung HZ35W is a 12-megapixel camera and the Sony SDC-WX1 is a 10.2-megapixel camera.

Video quality rankings

While its image quality was impressive, it was the iPhone 4’s video capabilities that really stole the show in our lab tests. Of the eight devices we rated for video, only the Flip Video M2120 scored higher. The Flip, which also records 720p, 30fps video, had just slightly better video quality than the iPhone 4, even in low-light. The Flip did have far superior audio quality when compared with the iPhone 4, which had the same audio score as the Droid X. The Samsung Galaxy had the best audio quality among the smartphones.

What it means

Apple said the quality of the camera parts is more important to capturing good photos than a high megapixel count. Our lab's test results support that theory, showing that a 5-megapixel camera can shoot higher quality images than an 8-megapixel camera.

For casual photographers who mostly post their images online, the iPhone 4’s bump in image quality might be enough to make them think twice before packing an additional gadget. Quality wise, it still isn’t quite on par with entry-level point-and-shoot cameras, but the iPhone's convenience (it’s already in your pocket), low-light capabilities, and access to a large amount of editing and sharing apps, could mean trouble for the inexpensive digital camera market.

For compact camcorder fans who own an iPhone, the iPhone 4’s great video quality makes it a no-brainer alternative to packing another single-use gadget like a Flip. On the other hand, buying a Flip doesn’t require a two-year contract and a data plan.

For anyone serious about image or video quality, or who knows a bit about photography and wants manual camera controls, the iPhone 4 still has a ways to go as a camera. As a camera built into a smartphone, however, it’s as good as they get.